Temporal variability in rill erodibility for two types of grasslands

The temporal variability in rill erodibility (K-r) and its influencing factors are not fully quantified in grasslands. This study was conducted to detect temporal variation and quantify the potential factors causing changes in rill erodibility by using natural, undisturbed soil samples collected from two grasslands and one bare soil near Beijing, China. Sampling was at similar to 20-day intervals from April to October 2011. Soil detachment capacity by concentrated flow was measured in a hydraulic flume with the fixed bed under six different flow shear stresses to determine rill erodibility. Root mass density was measured to analyse potential effects on temporal variability in rill erodibility. Mean rill erodibility of bare soil was 13.2 and 19.6 times greater than under switchgrass (Panicum virgatum) and smooth bromegrass (Bromus inermis). The temporal variability in rill erodibility under grasslands differed significantly from that of bare soil. Distinctive temporal variation patterns were found throughout the growing season. Rill erodibility declined as root density increased, and the rill erodibility of grassland could be well estimated from the measured erodibility of bare soil and root density (R-2 >= 0.92). The results of this study aid understanding of soil erosion mechanisms and development of process-based erosion models to simulate the seasonal variation in soil detachment by concentrated flow for grassland.